Replacing AC belt without belt tentioner

My have 745i 2005. it has no belt tentioner for Ac belt. Bmw use special tool for it,but i was too chep to pay $ 100 for it. I use my friend hands to hold the belt on the Ac pulley while i was crankg engine. It worked for me i put belt on Ac pulley less than 1 min . Here is proper way of doing that.

Thank you everyone who helped with sugestions of removing alternator and rest of the work. I finished mine yesturday. I changed Alternator,drive belt and Ac belt. I feel big defference now even my old belts were not bed at all.